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Veterinary Clinical Sciences Publications Veterinary Clinical Sciences

3-2-2021

Acute corneal hydrops of presumed traumatic origin: An uncontrolled case series (three horses)

Louise M. O'Leary Iowa State University, [email protected]

Lionel Sebbag Iowa State University

L. M. Moody University of Georgia and University of Tennessee

K. A. Diehl University of Georgia

Rachel A. Allbaugh Iowa State University, [email protected]

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Abstract This case series describes acute corneal hydrops in three young horses. Due to similarities in the clinical appearance and progression of the disease with that which is reported in humans and cats with acute corneal hydrops, traumatic Descemet’s membrane rupture was suspected to be the underlying aetiology in these equine cases. The horses presented with acute severe corneal oedema with intrastromal bullae formation and anterior bulging of the corneal contour. Focal posterior corneal changes were also seen in two of three cases. Mild anterior uveitis was also present. Other causes of corneal oedema (e.g. glaucoma) were ruled out based on presentation and clinical examination. Treatment approaches were medical and included various combinations of prophylactic topical antimicrobial therapy in case of secondary corneal ulceration, anti‐inflammatory therapy for uveitis, targeted oedema therapy with topical hypertonic saline and corneal cross‐linking, and placement of a temporary partial tarsorrhaphy for corneal tamponade. The outcome was excellent in all cases, with rapid resolution of the ocular changes. Acute corneal hydrops of presumed traumatic Descemet’s membrane rupture origin should be considered in cases of young horses presenting with acute corneal oedema. However, further studies are warranted to better characterise the disease and to try to confirm the suspected aetiology.

Keywords horse, bullous keratopathy, keratoconus, corneal oedema, ocular trauma, Descemet’s membrane rupture

Disciplines Large or Food Animal and Equine Medicine | Ophthalmology

Comments This is the published version of the following article: O’Leary, L. M., L. Sebbag, L. M. Moody, K. A. Diehl, and R. A. Allbaugh. "Acute corneal hydrops of presumed traumatic origin: An uncontrolled case series (three horses)." Equine Veterinary Education (2021). DOI: 10.1111/eve.13455. Posted with permission.

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This article is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/vcs_pubs/52 EQUINE VETERINARY EDUCATION 1 Equine vet. Educ. (2021) () - doi: 10.1111/eve.13455

Case Report Acute corneal hydrops of presumed traumatic origin: An uncontrolled case series (three horses) L. M. O’Leary†* , L. Sebbag†, L. M. Moody‡, K. A. Diehl‡ and R. A. Allbaugh† †Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa,; and ‡Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA *Corresponding author email: [email protected]

L. M. Moody's present address: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Tennessee, USA

Keywords: horse; bullous keratopathy; keratoconus; corneal oedema; ocular trauma; Descemet’s membrane rupture

Summary the disease is still poorly understood. Males and younger This case series describes acute corneal hydrops in three individuals tend to be predisposed in both species (Fan young horses. Due to similarities in the clinical appearance Gaskin et al. 2013; Pedersen et al. 2016). To the best of the and progression of the disease with that which is reported in authors’ knowledge, acute corneal hydrops has not been humans and cats with acute corneal hydrops, traumatic formally described in the horse although its existence has Descemet’s membrane rupture was suspected to be the been alluded to in veterinary textbooks without further underlying aetiology in these equine cases. The horses characterisation (Dubielzig et al. 2010; Brooks et al. 2017a). presented with acute severe corneal oedema with intrastromal The purpose of this case series is to describe the clinical bullae formation and anterior bulging of the corneal contour. findings, progression, treatment and outcome of three horses Focal posterior corneal changes were also seen in two of three with acute corneal hydrops, presumed to be secondary to cases. Mild anterior uveitis was also present. Other causes of traumatic Descemet’s membrane rupture. corneal oedema (e.g. glaucoma) were ruled out based on presentation and clinical examination. Treatment approaches Materials and methods were medical and included various combinations of prophylactic topical antimicrobial therapy in case of A retrospective review of the medical records from two secondary corneal ulceration, anti-inflammatory therapy for veterinary teaching hospitals was performed from January uveitis, targeted oedema therapy with topical hypertonic 2005 to July 2020. Search terms included ‘corneal hydrops’, saline and corneal cross-linking, and placement of a ‘bullous keratopathy’, ‘corneal oedema’, and ‘keratoconus’. temporary partial tarsorrhaphy for corneal tamponade. The Cases were excluded if clinical signs were present for more outcome was excellent in all cases, with rapid resolution of the than 2 weeks prior to presentation, if records were ocular changes. Acute corneal hydrops of presumed incomplete, if infectious keratitis was present (based on traumatic Descemet’s membrane rupture origin should be corneal cellular infiltrates and cytological or culture results), or considered in cases of young horses presenting with acute if other notable changes were present on ophthalmic corneal oedema. However, further studies are warranted to examination or ocular histopathology (eg severe uveitis, better characterise the disease and to try to confirm the glaucoma and retinal detachment). All cases were suspected aetiology. evaluated by a board-certified veterinary ophthalmologist. Data included age, breed, sex, presenting clinical signs, treatment and outcome. Nine cases met the inclusion Introduction criteria, but six of nine cases were excluded based on >1 Acute corneal hydrops is a severe manifestation of corneal aforementioned exclusion criteria. oedema where rapid, large accumulation of fluid results in gross thickening of the cornea and bullae formation. The Case details condition results in keratoconus, or anterior bulging of the cornea and can be vision- or globe-threatening if not Case 1 managed appropriately. Acute corneal hydrops is reported in A 2.5-year-old Paint gelding presented with severe corneal humans and cats and is caused by localised rupture of oedema of oculus sinister (OS) noted by the owner following Descemet’s membrane (Dubielzig et al. 2010; Fan Gaskin a reported ocular trauma several days prior at the trainer’s et al. 2013; Barsam et al. 2017; Schlesener et al. 2018), facility for which no treatments were administered. allowing ingress of aqueous humour with rapid and Abnormalities observed OS on presentation included mild progressive corneal hydration. Risk factors have been blepharospasm, marked diffuse corneal oedema with large suggested in humans (pre-existing ectatic corneal disease, intrastromal bullae axially and keratoconus (Fig 1a), and mild trauma) (Grewal et al. 2000; Barsam et al. 2017) and cats anterior uveitis characterised by 1 + flare, miosis and (systemic cyclosporine administration) (Pierce et al. 2016), but decreased intraocular pressure (8 mmHg vs 22 mmHg in

© 2021 The Authors. Equine Veterinary Education published by John Wiley & Sons Ltd on behalf of EVJ Ltd. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. 2 Presumed traumatic acute corneal hydrops

a) b) a) b)

Day 0 Day 2 Day 0 Day 10

c) d) Fig 2: Case 2: Clinical photographs of the affected OS. a) At initial examination, note the severe corneal oedema and axial bullae with keratoconus. b) By Day 10, there has been marked improvement of the corneal oedema with resolution of the keratoconus and bullae. Mild oedema and ﬁbrosis remain axially. The pupil is pharmacologically dilated.

Day 4 Day 6 The patient was hospitalised with a sub-palpebral lavage e) f) system. Medical therapy OS consisted of atropine sulfate1 1% q. 8 h, ofloxacin2 0.3% q. 6 h, diclofenac3 0.1% q. 6 h, 5% hypertonic saline (Muro 128)1 q. 6 h and oral flunixin meglumine (Banamine)4 1.1 mg/kg q. 12 h. After 48 h of therapy, corneal oedema improved but the large bulla continued to progress (Fig 1b) and became associated with fi Day 10 Day 13 a super cial corneal ulcer another 48 h later. At that time, the corneal epithelium was debrided with sterile cotton- tipped applicators and modified accelerated corneal cross- g) h) linking was performed under sedation (45 mW/cm2 for 2 min) (Famose 2014). The corneal hydrops continued to enlarge and cover the ventral cornea despite cross-linking, becoming progressively more flaccid in appearance (Fig 1c). Two days after cross-linking, the flaccid cornea contacting the lower eyelid was trimmed with Westcott scissors under topical Day 26 Day 45 anaesthesia and sedation (Fig 1d). Over the successive 10 days of hospitalisation, the corneal oedema and ulcer Fig 1: Case 1. Clinical photographs of the affected OS showing slowly resolved OS (Fig 1e), which revealed localised the progression of corneal hydrops. a) At the initial examination, note the severe diffuse corneal oedema and large axial disinsertion of the iris base laterally (iridodialysis). The patient intrastromal bulla formation leading to keratoconus. b) At Day 2, was discharged from the hospital with continued medical the oedema has markedly improved but the bulla has become therapy consisting of a tapering course of flunixin meglumine progressively more flaccid and migrated ventrally. c) By Day 4, per os,ofloxacin OS q. 8 h, serum OS q. 8 h, hypertonic saline the bulla had superficial fluorescein stain uptake. The corneal OS q. 8 h and atropine OS q. 24 h. Recheck examination 2 epithelium was debrided to allow corneal cross-linking weeks later showed axial superficial fibrosis and faint corneal fl (photograph was taken prior to cross-linking). d) The accid oedema at the site of the corneal hydrops, as well as lateral corneal bulla has been trimmed on Day 6, leaving behind an perilimbal endothelial fibrosis, mild oedema and thin irregular topography corneal defect. e) Day 10, the corneal neovascularisation of the cornea associated with the site of oedema has continued to improve with an axial irregularly- surfaced, ulcerated area of the cornea (where the flaccid cornea iridodialysis (Fig 1f). The patient was discharged with a 5 was trimmed) and residual lateral corneal oedema with mild tapering course of topical prednisolone acetate to reduce perilimbal neovascularisation. f) Day 13, fibrosis of the corneal corneal fibrosis (Fig 1g), and no recurrence of disease was defect is seen as a grey haze outlining the area of previous noted at the final recheck 6 weeks later (Fig 1h). corneal excision. The temporal oedema remains, and there is increased neovascularisation temporally. g) Day 26, fibrosis of the Case 2 site of previous large intrastromal bulla formation/corneal A 1-year-old Arabian filly presented with severe corneal excision has progressed and is moderate. The lateral oedema oedema OS. The lesion was first noted 4 days prior to referral, has receded further with a residual area of focal oedema, fibrosis was positive to fluorescein stain uptake, and progressed and neovascularisation covering the site of peripheral iridal rapidly despite management with oral flunixin meglumine per separation (iridodialysis). h) Day 45, the corneal fibrosis axially and temporal oedema are static to mildly improved. os q. 12 h (unknown dose) and topical oxytetracycline/ polymyxin B (Terramycin)6 OS q. 12 h. Abnormalities observed on presentation included mild blepharospasm, marked diffuse corneal oedema with an 8 mm 9 10 mm large oculus dexter (OD)). A small linear endothelial white opacity intrastromal bulla axially and keratoconus OS (Fig 2a), as well in the region of the large bullae was also noted OS. as mild anterior uveitis characterised by trace flare and Fluorescein uptake was negative oculus uterque (OU). miosis. Intraocular pressures were 12 mmHg OS and 15 mmHg

a) b) abrasions to the forehead and jaw-line, along with a small lip laceration. The horse was sedated, and a partial temporary tarsorrhaphy was placed with two interrupted horizontal mattress sutures 4-0 Nylon (Ethilon)8 to provide tamponade to the corneal hydrops. Medical treatment was initiated OS with neomycin-polymyxin-bacitracin q. 12 h, atropine q. 48 h, hypertonic saline q. 4–6 h, voriconazole 2% ophthalmic 9 Day 0 Day 10 ointment q. 12 h and oral flunixin meglumine on a tapering schedule. At recheck one week later, the tarsorrhaphy Fig 3: Case 3: Clinical photographs of the affected OS. a) At sutures were removed revealing resolution of the corneal presentation with focal severe corneal oedema resulting in early hydrops and fibrin. Minimal residual corneal oedema was keratoconus. The pupil has been pharmacologically dilated. b) present (Fig 3b). All medications were discontinued at that At recheck 10 days later, note the resolution of the corneal time, and no recurrence of disease was reported by the oedema and keratoconus with very mild residual fibrosis. owner (phone update at 9 months).

Discussion

OD. No corneal infiltrates were seen. Fluorescein uptake was The present case series highlights the clinical presentation, negative. Corneal cytology and aerobic bacterial culture therapeutic plan and clinical outcomes of three young were taken. The cytology revealed mild neutrophilic horses diagnosed with acute corneal hydrops of presumed inflammation with no infectious organisms and the culture traumatic origin. Early recognition and prompt management was negative, suggestive of a sterile process. of this uncommon condition can result in excellent clinical Though corneal sampling did not yield infectious outcomes, as described herein. organisms, the patient was hospitalised with a sub-palpebral Several features suggest a traumatic aetiology with lavage system, and aggressive antimicrobial therapy was resulting Descemet’s membrane rupture and development of initiated OS based on disease severity and inability to acute corneal hydrops. First, each young horse was likely definitively rule out infection: ofloxacin q. 4 h, ‘green’, two of the three horses were in active training, and chloramphenicol7 0.5% ophthalmic solution q. 4 h, all three horses had their OS affected, consistent with voriconazole7 1% ophthalmic solution q. 4 h, serum q. 4 h, handlers typically working with horses from their left side. An atropine q. 12 h and flunixin meglumine 1.1 mg/kg per os q. injury to the eye of Case 1 was specifically reported by the 12 h. Improvement in corneal hydrops was rapid, with a trainer, but no details were provided; however, the notable decrease in the size of the large bulla to disinsertion of the lateral iris base in Case 1 is consistent with 5mm9 7 mm by the next day. On Day 4 of hospitalisation, blunt trauma (Brooks et al. 2017b). Further, focal endothelial topical antimicrobials and serum were decreased in opacities were detected in two horses, consistent with frequency to three times daily, and atropine and flunixin traumatic Descemet’s membrane rupture, suggested by a meglumine were tapered due to the continued marked linear endothelial lesion (Brooks et al. 2017a, 2017b; Rodriguez improvement. Within 10 days of presentation, all medications Galarza and McMullen 2020) in Case 1 and fibrin adhered to were discontinued, the bulla had resolved and the residual the endothelial opacity in Case 3 (Ledbetter and Gilger oedema was minimal. A focal area of fibrosis was present 2013), with concomitant worse oedema compared to the where the bulla and hydrops had been present (Fig 2b). The surrounding cornea without endothelial changes. patient was discharged without any medications, and no Second, the severity, progressive and peracute nature of recurrence of disease was reported by the owner (phone the oedema was consistent with Descemet’s membrane update at one year). rupture, as reported in human and feline cases of acute corneal hydrops (Grewal et al. 2000; Pederson et al. 2016). Case 3 Although blunt trauma is not considered to play a role in A 1-year-old Warmblood colt presented with acute corneal feline acute corneal hydrops (Pederson et al. 2016), it is oedema OS of less than 24 h duration. The eye was recognised as an inciting event for acute corneal hydrops in diagnosed with a corneal ulcer and corneal oedema by the humans (Grewal et al. 2000; Fan Gaskin et al. 2013). referring veterinarian, who prescribed atropine q. 24 h OS Third, other differentials for severe corneal oedema in and neomycin-polymyxin-bacitracin1 OS q. 8 h and horses (eg uveitis, glaucoma, endotheliitis, heterochromic administered a single 1 mg/kg dose of intravenous flunixin iridocyclitis with secondary keratitis and corneal infection) meglumine. The patient was referred 12 h later due to (Pinto et al. 2015; Brooks et al. 2017a; Slenter et al. 2020) were significant lesion progression. Abnormalities observed on ruled out based on the history, comprehensive ophthalmic presentation OS included mild blepharospasm and marked examination and response to therapy in each case. focal corneal oedema with mild keratoconus (Fig 3a). The Taken together, rupture of Descemet’s membrane is the left pupil was pharmacologically dilated from atropine most plausible explanation for the corneal hydrops in the administration. No corneal infiltrates were seen. Pin-point cases described in this report, although this suspicion was not fluorescein uptake was present over the corneal bullae. A confirmed with advanced diagnostics. Optical coherence small amount of fibrin was noted to be adherent to the tomography and ultrasound biomicroscopy are two imaging corneal endothelium in the region of the bullae, and trace modalities used to detect Descemet’s membrane rupture in flare was present. The patient also had several small cuts and humans, cats and horses (Grewal et al. 2000; Matas Riera

et al. 2015; Schlesener et al. 2018; Rodriguez Galarza and management alone may suffice, the use of a temporary McMullen 2020); unfortunately, such imaging modalities were tarsorrhaphy to tamponade the corneal hydrops could not available to the authors at the time of each case accelerate healing. Additional work is required to better management. Conventional ocular ultrasound can be characterise this condition in horses and optimise clinical considered for cases with large Descemet’s membrane management. separations in horses (Matas Riera et al. 2015; Slenter et al. 2020), although this imaging tool may not be sensitive Authors’ declaration of interests enough to detect a focal Descemet’s membrane rupture. Attempts to confirm the suspicion of Descemet’s membrane No conflicts of interest have been declared. rupture using optical coherence tomography or ultrasound biomicroscopy are suggested in future cases of equine acute Ethical animal research corneal hydrops. Acute corneal hydrops requires rapid and targeted Case report therefore no ethical approval needed. therapy to avoid vision- or globe-threatening complications such as corneal rupture, as described in human and feline Source of funding patients (Grewal et al. 2000; Pederson et al. 2016). In fact, three of nine horses originally identified in the medical record Owner funded clinical cases. No funding provided. search (excluded from further consideration for reasons as above) were enucleated due to painful corneal hydrops Authorship complications including recurrent corneal ulceration from bullae rupture and corneal perforation. It is likely that early L. O’Leary as the primary author contributed to the case and aggressive management of those cases would have collection, case series design, data analysis and preparation achieved a positive outcome. In contrast, the three horses of the manuscript. K. Diehl, L. Sebbag and R. Allbaugh described in this case series had excellent outcomes despite contributed to case management and assisted in study diverse treatment approaches, utilising medical design and manuscript preparation. L. Moody contributed to management Æ corneal cross-linking or temporary case collection, data analysis, and assisted in study design tarsorrhaphy. Although corneal cross-linking was performed in and preparation of the manuscript. All authors gave the Case 1, it did not appear to reverse the corneal changes or manuscript their final approval. halt progression, possibly due to limited penetration of fl ribo avin and subsequent UV-A stimulus in the thickened Manufacturers’ addresses oedematous equine cornea (Gallhoefer et al. 2016). Aggressive medical management was initiated with 1Bausch and Lomb, Rochester, New York, USA. 2 antimicrobials for Case 2 pending culture results; although Hi-Tech Pharmacal, Amityville, New York, USA. 3Akorn Inc., Lake Forest, Illinois, USA. bacterial and fungal cultures were negative, the possibility of 4Schering-Plough Animal Health, Kenilworth, New Jersey, USA. previous infection could not be entirely ruled out given the 5Sandoz, Holzkirchen, Germany. use of broad-spectrum antibiotics prior to presentation and 6Zoetis, Florham Park, New Jersey, USA. 7 corneal sampling. Case 3 was treated with a temporary Compounded from Iowa State University College of Veterinary Medicine’s pharmacy, Ames, Iowa, USA. tarsorrhaphy to provide tamponade to the bulging cornea, 8Ethicon, Somerville, New Jersey, USA. similar to the most effective treatment reported in cats with 9Compounded from University of Georgia College of Veterinary acute corneal hydrops (Pederson et al. 2016). This patient’s Medicine’s pharmacy, Athens, Georgia, USA. disease was mild in comparison to the other two cases described in this report, suspected to be due to the prompt References referral (the patient presented within 24 h) and tamponade of the developing corneal hydrops. The condition resolved Barsam, A., Brennan, N., Petrushkin, H., Xing, W., Quartilho, A., Bunce, C., Foot, B., Cartwright, N.K., Haridas, A., Agrawal, P., Suleman, H., within 7 days in this patient. The authors advise clinicians to Ahmad, S., MacDonald, E., Johnston, J. and Tuft, S. (2017) Case- consider temporary tarsorrhaphy or a third eyelid flap control study of risk factors for acute corneal hydrops in (Pederson et al. 2016) as adjunctive tools in the management keratoconus. Br. J. Ophthalmol. 101, 499-502. of acute corneal hydrops in horses, although additional cases Brooks, D.E., Matthews, A. and Clode, A.B. (2017) Diseases of the and prospective case studies are required to confirm the cornea (supplementary material). In: Equine Ophthalmology, 3rd potential benefits of these procedures. Other options such as edn., Ed: B. Gilger, Wiley-Blackwell, Maryland Heights, Missouri. corneal welding may be considered in nonresponsive or Brooks, D.E., Matthews, A. and Clode, A.B. (2017) Diseases of the chronic cases (Rodriguez Galarza and McMullen 2020). cornea. In: Equine Ophthalmology, 3rd edn, Ed: B. Gilger, Wiley Blackwell, Maryland Heights, Missouri. pp 252-368. Dubielzig, R.R., Ketring, K., McLellan, G.J. and Albert, D.M. (2010) Conclusions Diseases of the cornea and sclera. In: Veterinary Ocular Pathology, 1st edn, Eds: R.R. Dubielzig, K. Ketring, G.J. McLellan Acute corneal hydrops is an uncommon condition affecting and D.M. Albert, W.B. Saunders, St. Louis. pp 201-243. ’ horses. Presumptive trauma causing Descemet s membrane Famose, F. (2014) Evaluation of accelerated collagen cross-linking for rupture was suspected in the horses in this case series given the treatment of melting keratitis in eight dogs. Vet. Ophthalmol. the predilection for young horses and those in training. 17, 358-367. Clinical outcome is expected to be excellent with early Fan Gaskin, J.C., Good, W.R., Jordan, C.A., Patel, D.V. and McGhee, recognition and therapeutic intervention. Although medical C.N.J. (2013) The Auckland keratoconus study: identifying

predictors of acute corneal hydrops in keratoconus. Clin. Exp. association between systemic cyclosporine administration and Optom. 96, 208-213. development of acute bullous keratopathy in cats. Vet. Gallhoefer, N.S., Spiess, B.M., Guscetti, F., Hilbe, M., Hartnack, S., Ophthalmol. 19, Suppl. 1, 77-85. Hafezi, F. and Pot, S.A. (2016) Penetration depth of corneal cross- Pinto, N.I., McMullen, R.J., Linder, K.E., Cullen, J.M. and Gilger, B.C. linking with riboflavin and UV-A (CXL) in horses and rabbits. Vet. (2015) Clinical, histopathological and immunohistochemical Ophthalmol. 19, 275-284. characterization of a novel equine ocular disorder: heterochromic Grewal, S., Laibson, P., Cohen, E. and Rapuano, C. (2000) Acute iridocyclitis with secondary keratitis in adult horses. Vet. Ophthalmol. 18, 443-456. hydrops in the corneal ectasias: associated factors and outcomes. Am. J. Ophthalmol. 129, 702-703. Rodriguez Galarza, R.M. and McMullen, R.J. (2020) Descemet’s membrane detachments, ruptures, and separations in ten adult Ledbetter, E.C. and Gilger, B.C. (2013) Diseases and surgery of the cornea and sclera. In: Veterinary Ophthalmology, Ed: B. Gilger, T. Kern horses: Clinical signs, diagnostics, treatment options, and preliminary results. Vet. Ophthalmol. 23, 611-623. and K. Gelatt, Lippincott Williams & Wilkins, Baltimore. pp 675-700. Schlesener, B.N., Scott, E.M. and Vallone, L.V. (2018) An unusual case Matas Riera, M., Donaldson, D. and Priestnal, S.L. (2015) Descemet’s of feline acute corneal hydrops: atypical disease presentation membrane detachment in horses; case series and literature ’ review. Vet. Ophthalmol. 18, 357-363. and possible in vivo detection of Descemet s membrane detachment in the cat’s unaffected eye. Vet. Ophthalmol. 21, Pederson, S.L., Pizzirani, S., Andrew, S.E., Pate, D.O., Stine, J.M. and 426-431. Michau, T.M. (2016) Use of a nictitating membrane flap for Slenter, I.J.M., Hermans, H., Ensink, J.M., Willems, D.S., Veraa, S., Grinwis, treatment of feline acute corneal hydrops-21 eyes. Vet. Ophthalmol. 19, Suppl. 1, 61-68. G.C.M. and Boeve, M.H. (2020) Clinical, ultrasonographic, and histopathologic findings in seven horses with Descemet’s Pierce, K.E., Wilkie, D.A., Gemensky-Metzler, A.J., Curran, P.G., membrane detachment: A case series. Vet. Ophthalmol. 23, 181- Townsend, W.M., Petersen-Jones, S.M. and Bartoe, J.T. (2016) An 189.